#include <iostream>
#include <algorithm>
#include <cmath>

using namespace std;
// 精度要到1e-9才行？
const double inf = 1e-9;


int main()
{
    double n;
    cin >> n;
    double l = -1000, r = 1000;
    while(l < r)
    {
        double mid = (l + r) / 2;
        double tmp = pow(mid, 3);
        if(abs(tmp - n) < inf)
        {
            printf("%.6lf", mid);
            return 0;
        }
        if(tmp > n) r = mid;
        else l = mid;
    }
    return 0;
}